180 or 190 rear tyre?

i could be wrong, i usually am, but i thought the dunlop 55 was constructed so it didn't alter the radius, so the speedo will still be ok...????

 

Yes that's true buddy... the speedo shouldn't be affected by the tyre fitted.

 

You may well be right there, but I'm struggling with the logic. If the tyre is taller by 5%, then the rolling circumference is X % more, hence the change in final drive gearing. Does the Dunlop have a lower sidewall?

 

The 55 profile defintely has a larger diameter, that's part of the point. It raises the rear end which helps turn in.

This document is interesting, it sets out a standard for tyre sizes.

http://www.stevenott.com/draft5751.pdf

According it these are the diameters of the two sizes in question:

190/50-17 622mm
190/55-17 642mm

Using the Gearing Commander website Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator going two up on the rear spocket will compensate.
Which is why I've got a 44 Tooth Renthal sprocket which arrived today

 

Changing to a 44 rear sprocket and sticking with the 50 profile is more fun in some ways though

 

If you have a spare hour or so & want to learn a little about the differences between tyre brands, this Dave Moss film is interesting.

E.g. I have never got on with Dunlop tyres; don't like the feel. Dave demonstrates that dunlops give a high amount of feedback because they are so stiff; to much feedback for me - distracting even. Conversley, he shows why the Pirelli are designed to give less feedback & a better contact patch - my prefered brand.

He also shows that tyres of the same size, but different brands, can be very different indeed. You could even say that a Pirelli 190/50 is the same size as a Dunlop 190/55. Strange init.

Dave Moss Unsprung: Tires, Dave discusses one of the most forgotten pieces of motorcycle suspension, the tires. He explores tire profiles, carcass construc...

 

this is 1 of my personal favourite tyre videos, really helped me choose the tyre i wanted

 

Best for economy I have used were pilot sports - even used them on track with no issues and now gone for pilot power 190/55 but not the 2ct's. Reason being they are £60 cheaper and the only difference is the 2ct's have softer edges. Unless your riding track days in the inters you don't need that soft.

Got mine on eBay for around £160 delivered and love them